Bergey disclosed a solid state watch display switch in U.S. Pat. No. 3,871,170 in which an arm responsive switch is provided for actuating the display in response to a predetermined movement of the wearer's arm. However, such a switch should be actuated by moving a carrier's arm to mechanically operate an LED display to show a watch time, which is not suitably applicable for a clock since the clock is always hanged on a fixed position.
Bui et al disclosed a speech-controlled electronic watch in U.S. Pat. No. 4,635,286 comprising an electro-acoustic means for converting a pronounced word into an analog signal representing that word, means for transforming the analog signal into a logic control information and means for transforming the logic information into a control signal, such as for controlling a display means of a watch. However Bui's watch still requires a complex structure, a great number of components and higher production cost therefor. It must be effected by a human speech and will not be operated if someone is dumb who cannot give a speech signal to the electro-acoustic system of Bui's device.
The present inventor has found the drawbacks of a conventional watch or timepiece and invented the present digital clock which is actuated by human's clap.